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https://issues.apache.org/jira/browse/HDFS-3150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13433724#comment-13433724
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Aaron T. Myers commented on HDFS-3150:
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The trunk patch looks pretty good to me. One little comment:
bq. @param useHostname if "name" should use a hostname or IP
This comment reads a little funny. Maybe "true to use the hostname of the DN,
false to use the IP address."
+1 once this is addressed.
> Add option for clients to contact DNs via hostname
> --------------------------------------------------
>
> Key: HDFS-3150
> URL: https://issues.apache.org/jira/browse/HDFS-3150
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: data-node, hdfs client
> Affects Versions: 1.0.0, 2.0.0-alpha
> Reporter: Eli Collins
> Assignee: Eli Collins
> Fix For: 1.1.0
>
> Attachments: hdfs-3150-b1.txt, hdfs-3150-b1.txt, hdfs-3150.txt,
> hdfs-3150.txt, hdfs-3150.txt
>
>
> The DN listens on multiple IP addresses (the default {{dfs.datanode.address}}
> is the wildcard) however per HADOOP-6867 only the source address (IP) of the
> registration is given to clients. HADOOP-985 made clients access datanodes by
> IP primarily to avoid the latency of a DNS lookup, this had the side effect
> of breaking DN multihoming (the client can not route the IP exposed by the NN
> if the DN registers with an interface that has a cluster-private IP). To fix
> this let's add back the option for Datanodes to be accessed by hostname.
> This can be done by:
> # Modifying the primary field of the Datanode descriptor to be the hostname,
> or
> # Modifying Client/Datanode <-> Datanode access use the hostname field
> instead of the IP
> Approach #2 does not require an incompatible client protocol change, and is
> much less invasive. It minimizes the scope of modification to just places
> where clients and Datanodes connect, vs changing all uses of Datanode
> identifiers.
> New client and Datanode configuration options are introduced:
> - {{dfs.client.use.datanode.hostname}} indicates all client to datanode
> connections should use the datanode hostname (as clients outside cluster may
> not be able to route the IP)
> - {{dfs.datanode.use.datanode.hostname}} indicates whether Datanodes should
> use hostnames when connecting to other Datanodes for data transfer
> If the configuration options are not used, there is no change in the current
> behavior.
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